Is this relay for your server to send mail out, or is it to allow an external server/user to send mail through to your server? The difference is if you require a SEND or a RECEIVE connector.

It does not require downtime to do this.

In the properties of the connector there is an area to set the IP Address for relaying if you need that. In the Hub transport area for the receive connectors. Go to properties, then look on the network tab.

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